The phosphatidylglycerol/cardiolipin biosynthetic pathway is required for the activation of inositol phosphosphingolipid phospholipase C, Isc1p, during growth of Saccharomyces cerevisiae
The phosphatidylglycerol/cardiolipin biosynthetic pathway is required for the activation of inositol phosphosphingolipid phospholipase C, Isc1p, during growth of Saccharomyces cerevisiae
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DOI：
10.1074/jbc.m411058200
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发表时间：
2005-02-25
影响因子：
4.8
通讯作者：
Hannun, YA
中科院分区：
文献类型：
--
作者：
de Avalos, SV;Su, XF;Hannun, YA
肌鞘脂磷脂酶C （Isc1p）是酿酒酵母中性鞘磷脂酶大家庭的成员，调节生物活性神经酰胺的产生。最近，我们报道了Isc1p在生长后双氧期被翻译后激活，并且它定位于线粒体（Vaena de Avalos， S., Okamoto， Y., and Hannun， Y. A. (2004) J.生物化学，279,11537-11545）。本研究探讨了Isc1p在体内的激活机制和功能。ISC1的缺失导致非发酵碳源的生长明显降低。有趣的是，isc1Delta菌株的生长缺陷与pgs1Delta菌株相似，缺乏在体外激活Isc1p的磷脂酰甘油（PG）和心磷脂（CL）合成的承诺步骤。因此，我们研究了Pgs1p在体内激活Isc1p中的作用。结果表明，在pgs1Delta菌株中，Isc1p的生长依赖性激活和植物神经酰胺水平在双氧化后阶段的isc1依赖性增加受到损害，这表明体内Isc1p的激活依赖于PGS1和线粒体磷脂PG/CL。从机制上说，Isc1p的缺失导致线粒体细胞色素c氧化酶亚基cox3p和cox4p水平降低，这是先前确定的PG和CL的靶标(Ostrander， D. B., Zhang， M., Mileykovskaya， E., Rho， M., and Dowhan， W. (2001) J. Biol。化学，276,25262-25272)，因此表明Isc1p至少介导PG/CL下游的一些功能。本研究首次为Isc1p的体内活化机制和功能提供了证据。提出了一种内源性PG/CL作为体内Isc1p激活剂的模型。
Inositolsphingolipid phospholipase C (Isc1p) is the Saccharomyces cerevisiae member of the extended family of neutral sphingomyelinases that regulates the generation of bioactive ceramides. Recently, we reported that Isc1p is post-translationally activated in the post-diauxic phase of growth and that it localizes to mitochondria (Vaena de Avalos, S., Okamoto, Y., and Hannun, Y. A. (2004) J. Biol Chem. 279,11537-11545). In this study the in vivo mechanisms of activation and function of Isc1p were investigated. Deletion of ISC1 resulted in markedly lower growth in non-fermentable carbon sources. Interestingly, the growth defect of isc1Delta strains resembled that of pgs1Delta strains, lacking the committed step in the synthesis of phosphatidylglycerol (PG) and cardiolipin (CL), which were shown to activate Isc1p in vitro. Therefore, the role of Pgs1p in activation of Isc1p in vivo was investigated. The results showed that in the pgs1Delta strain, the growth-dependent activation of Isc1p was impaired as was the ISC1-dependent increase in the levels of phytoceramide during the post-diauxic phase, demonstrating that the activation of Isc1p in vivo is dependent on PGS1 and on the mitochondrial phospholipids PG/CL. Mechanistically, loss of Isc1p resulted in lower levels of mitochondrial cytochrome c oxidase subunits cox3p and cox4p, previously established targets of both PG and CL (Ostrander, D. B., Zhang, M., Mileykovskaya, E., Rho, M., and Dowhan, W. (2001) J. Biol. Chem. 276, 25262-25272), thus suggesting that Isc1p mediates at least some functions downstream of PG/CL. This study provides the first evidence for the mechanism of in vivo activation and function of Isc1p. A model with endogenous PG/CL as the in vivo activator of Isc1p is proposed.